1. Field of the Invention
The present invention pertains to current sensing of a piece of power supply equipment generating direct-current voltage, and in particular, to technology valid for improving the current sensing accuracy in a power supply driver circuit driving a power transistor by means of switching control.
The power supply driver circuit of the present invention is suited to a power supply driver circuit driving the power transistors of a piece of switched-mode power supply equipment controlling switching, e.g. with the PWM (Pulse Width Modulation) method, converting an input voltage, and obtaining an output voltage, and to a driver module equipped with the circuit, as well as to a switched-mode power supply utilizing the module.
2. Description of the Related Art
When it comes to electronic equipment in recent years, articles equipped with a microprocessor (below called CPU, Central Processing Unit) as a system control device have become more frequent. Also, there is a trend that the operating frequency of CPUs is becoming higher and higher, the increase in operating frequency being accompanied by an increase in maximum operating current.
Accordingly, in order to respond to the demand for these large currents, multi-phase systems which raise the current supply capacity by connecting multiple switching power supplies in parallel are being proposed.
In this kind of power supply systems, it is necessary to sense the current flowing in the coil and to control by feedback the drive signal of the power transistor of each phase so that a uniform current is flowing for each power supply (phase).
Because the current of each phase is uniformly controlled in the current sensing for feedback control, a relatively high accuracy is required.
As a method for sensing currents with high accuracy in power supply systems of this kind, there is e.g. the method set out in JP-A-2003-232816.